This invention relates to a hydrosteering device of the rack and pinion type adapted for use in automotive vehicles such as that disclosed in a prior copending application owned in common with the present application, now U.S. Pat. No. 4,275,641 to Kopp.
In a hydrosteering device of the foregoing type, a spur gear rack driven by a steering pinion is mounted by bearings in a steering gear housing. A piston ring having an outer annular seal and at least one radially inner elastic sealing ring resiliently mounting the piston ring in the rack, separate inner and outer pressure chambers within the housing. The toothed portion of the rack is disposed within the housing while the remaining portion of the rack extends through a cylindrical tube extension of the housing.
In such a hydrosteering device, the cylindrical tube extension serves as an operating piston chamber with a servo piston mounted on the rack to form inner and outer pressure spaces within the tube extension. One problem arising with such arrangements is the lack of a reliable piston seal because of misalignments and flexural moments. For this reason, an axially floating piston mounting has been proposed to balance out misalignments and flexural moments. Thus, the piston ring carrying the outer annular seal is connected to the rack through an elastic inner sealing ring. The piston ring is axially fixed to the rack by two snap rings. Therefore, the piston is not capable of absorbing large axial forces.
It is therefore an important object of the present invention to provide a rack and pinion type of hydrosteering device wherein misalignments and flexural moments are balanced out by an improved piston arrangement which also reduces space requirements.